Quantitative X-ray Diffraction Techniques Research Articles

Interfaces in titanium-titanium boride composites: H.W.Jeong, Y.T.Lee. (Korea Inst. of Machinery and Materials, Changwon, Korea.) J. Korea Inst. Met. Mater., vol 37, no 1, 1999, 57–63. (In Korean.)

Single crystals of metastable BCC Ti-6.5 at.% Mo alloy have been aged at 350°C for varying times to precipitate the omega phase. The variation in volume fraction of precipitate was determined by a quantitative X-ray diffraction technique and correlated with transmission electron microscopy from thin foils. For Ti-Mo alloys the lattice misfit between omega and beta phases is small; reflections from parallel planes of both phases overlap necessitating the use of reflections from nonparallel planes. The 310 beta reflection and 3141 and 3032 omega reflections were selected. These two omega reflections occurred at 96° and 105° 2θ angles with CuKα radiation and required a 14° reorientation of the crystal.

Characterization of black rust staining of unpassivated 55% Al–Zn alloy coatings. Effect of temperature, pH and wet storage

Wet storage staining is a phenomenon that occurs on both zinc coated and 55% Al–Zn coated steel sheets during shipment or storage in damp conditions. Whereas zinc coated sheets form white corrosion products, 55% Al–Zn coated steel sheets form black corrosion products. The effect of temperature, pH and wet storage on the occurrence of black rust staining of unpassivated Aluzink samples has been investigated in the laboratory in terms of corrosion product formation and composition. A characterization of corrosion products formed has been performed mainly based on scanning electron microscopy with X-ray microanalyses (SEM/EDS) for morphological and quantitative analyses and X-ray diffraction techniques (XRD) for crystalline phase identification. Black rust formation is strongly related to alkaline pH regions and is enhanced by the temperature. All black panels show the presence of Bayerite (Al(OH) 3), mainly formed on the aluminum rich dendrite branches and a basic zinc aluminum carbonate (Zn 6Al 2(OH) 16CO 3·4H 2O) formed in the zinc rich interdendritic alloy regions in contact with air. Blackening of Aluzink surfaces is connected to differences in optical properties of embedded metallic zinc and/or aluminum particles of different shape and size in the corrosion layer.

Stress induced phase transformation of a cesium stabilized leucite porcelain and associated properties

Objectives. The addition of Cs 2O to dental porcelains might provide a means for controlling the thermal expansion and toughness of feldspathic porcelains. The purpose of this investigation was to determine for a leucite porcelain the effect of Cs 2O content upon its coefficient of thermal expansion (α), toughness, hardness, and content of low (tetragonal) leucite and high (cubic) leucite. Methods. In order to determine the amount of low leucite in the specimens, an x-ray calibration curve for low leucite and an internal standard of copper was obtained using quantitative x-ray diffraction techniques. Utilizing a stress induced phase transformation between low and high leucite, an x-ray intensity conversion ratio ( r) was determined for high leucite so that the calibration curve for low leucite could be used to determine the amount of high leucite present in the experimental porcelains. Specimens were prepared with various amounts of Cs 2O (0.0, 0.5, 1.0, 1.5, 2.0 mol%) so that, except for the as-received porcelain (A), all had the same thermal history. Specimens were tested for content of low and high leucite, hardness (Vickers), toughness (indentation-strength method), and coefficient of thermal expansion (α) over two temperature ranges (30–500°C and 30–640°C). Fractured surfaces were examined with a scanning electron microscope (SEM). For each property, specimen groups were compared for statistical differences. These comparisons were statistically analyzed using analysis of variance (ANOVA) and Fisher's protected least significant differences (PLSD). Results. Quantitative x-ray examination of abraded and heat-treated specimens demonstrated that a stress induced phase transformation occurred which could be reversed by heat treatment. The conversion ratio was determined as r=1.93±0.29. The addition of Cs 2O lowered the wt% of low leucite from 63±6% to 0% and increased the amount of high leucite from 0% to 62±5%. ANOVA showed that the addition of Cs 2O had a significant effect on α ( p<0.0001), hardness ( p<0.005), and toughness ( p<0.0001). Cs 2O significantly (PLSD) lowered the α ( p<0.0001), hardness ( p<0.01), and toughness ( p<0.0001) of a high-content leucite porcelain. Significance. A stress induced phase transformation of high leucite to low leucite was demonstrated and, as a consequence, suggested the potential for phase transformation toughening. The α of a leucite porcelain could be controlled by stabilizing high (cubic) leucite to room temperature with the fraction of high leucite dependent upon the amount of Cs 2O added. A method was developed to determine the amount of high leucite present in a porcelain.

Quantification of the minor precipitates in UDIMET™ alloy720(LI) using electrolytic extraction and X-ray diffraction

A study on the quantification of the minor precipitates such as σ-phase, carbide and boride in UDIMET™ alloy720 (U720) and alloy720LI (U720LI) was carried out. A quantitative X-ray diffraction technique combined with electrolytic extraction has been used to quantify the micro-constituents. It was shown that U720LI is much less prone to σ formation than U720. At 800 oC, the weight fraction of σ in U720LI remained at a level as low as ≈0.1%, even after 3000 h of exposure. In U720, on the contrary, it increased remarkably with exposure up to 1000 h and then saturated at ≈5%. A close examination of the σ formation mechanism using transmission electron microscopy (TEM), shows that σ forms and grows in consumption of γ′-phases. M 23C 6-type carbide and M 3B 2-type boride precipitates did not show any significant variations of amount in both alloys, U720LI and U720, during long time exposure at 800 oC.

A Quantitative X-Ray Diffraction Technique for Analyzing Sedimentary Rocks and Soils

Abstract Mineralogical studies of sedimentary rocks or sedimentary deposits are often required for engineering geological projects. X-ray diffraction analytical techniques are usually employed for this purpose but these methods are often complex and involved. Several different X-ray diffraction methods are described and a single suitable procedure is chosen and described in detail. The chosen method includes analysis of both clay and non-clay minerals and qualitative and quantitative interpretation.

Model for precipitation in polycrystalline Cu-11.55 at %-Be-0.23 at %-Co

The precipitate structure and matrix deformation were examined in a commercial Cu-11.55 at %-Be-0.23 at %-Co alloy by quantitative X-ray diffraction techniques. A model is proposed that is consistent with early electron microscopy results by Bonfield and Edwards [J. Mater. Sci. 9 (1974) 398] and recent advances by Khachaturyan and Laughlin [Acta Metall. Mater. 38 (1990) 1823]. Agreement was found for a precipitate model consisting of highly deformed versions of the equilibrium γ-phase. This is in accord with earlier results for γ″ and γ′ precipitates and is further generalized to include the GP zone for this alloy. Two states of deformation are required, i.e. one relatable to γ″ and the GP zone, with a second relatable to a continuous deformation which describes the rotation of the γ′ precipitate. The matrix becomes and remains severely deformed prior to and through the hardness maximum. Bragg-like matrix peaks become partitioned into three components: quasilines, static diffuse scattering and a residual Bragg peak. The so-called “arrowhead” scattering should be re-examined as a generalized form of Laue scattering, which includes a difference between the square of the scattering amplitudes for the precipitate and the matrix that it replaces.

Intermediate Si-Al spinel phase formation in phase transformation of diphasic mullite gel

Al2O3-SiO2 diphasic mullite gel (Si/Al=1/3) has been synthesized by using Al(NO3)3·9H2O and Ludox in basic conditions. Its phase transformation behaviour has been studied by qualitative and quantitative X-ray diffraction techniques. The results indicate that a noncrystalline alumino-silicate phase forms together with the slow crystallization of Si-Al spinel phase of a mullite-like composition up to 1250 °C. Thereafter, it transforms suddenly to orthorhombic mullite around 1325 °C. Earlier studies, e.g. alkali leaching, and measurement of co-ordination number of aluminium in 1000 °C heated diphasic gel, confirm Si-Al spinel formation as an intermediary phase.

Kinetics of Transition of Anhydrous Carbamazepine to Carbamazepine Dihydrate in Aqueous Suspensions

When suspended in water, anhydrous carbamazepine (C15H12N20; 1) was transformed to carbamazepine dihydrate (C15H12N20 • 2HzO; 2). Compound 1 was dispersed in water at 25 °C, and an aliquot of the slurry was taken at periodic intervals and immediately filtered under conditions which removed all the physically bound water from the solid. The weight fractions of 1 and 2 in the solid were quantified by two methods: (a) by determining the weight loss on drying the solid at 60 °C under reduced pressure to a constant weight and (b) by a quantitative powder X-ray diffraction technique. There was good agreement between the above two methods. More than 95% (w/w) of 1 was converted to 2 in 1 h and the decrease in the weight fraction of 1 with time was approximately a first-order process.

Sources of error in low temperature plasma ashing procedures for quantitative mineral analysis of coal ash

Using low temperature ashing in an oxygen plasma, the mineral matter in coals can be isolated and studied. A quantitative X-ray diffraction (XRD) technique has been developed, using accepted procedures, for the analysis of minerals (illite, gypsum, kaolinite, quartz, ankerite and pyrite) in low temperature coal ash (LTA). This XRD method should theoretically produce mineral totals approaching 100%, unless non-crystalline material is present. However, working with material ashed to constant weight gave mineral totals of between 50% and 80%; totals generally being lowest when the ash content of the coal was low. Further work showed that this shortfall was due to residual organic matter that can be removed by repeated fine-grinding and ashing.

The atomic structure of the Σ = 13( θ = 22.6°)[001] twist boundary in gold determined using quantitative X-ray diffraction techniques

Quantitative X-ray diffraction techniques have for the first time determined the complete three-dimensional atomic structure of a grain boundary. The structure of a large angle Σ = 13( θ = 22.6°)[001] twist boundary in Au was obtained with a resolution of ±0.06 Å or better normal to the interface and ±0.02 Å or better parallel to the interface. The atomic coordinates were determined by fitting a model structure to the intensity observations from large portions of the three-dimensional reciprocal lattice using a χ 2 analysis. Details of the atomic structure of the grain boundary, including the magnitude of the decrease in density at the interface, are presented. The grain boundary structure was shown to consist of arrays of distorted octahedra that bridge the interface in the regions of good fit between the two misoriented crystals, and special configurations of distorted tetrahedra, octahedra and Archimedean antiprisms located between the regions of good fit within the interface. The polyhedral construct is used to predict sites for, and concentrations of solute atoms that segregate to interstitial positions within the boundary, without causing appreciable distortion of the boundary structure.

Quantitative X-ray diffraction study of the atomic structure of the ∑ = 5( θ = 36.9°) [001]twist boundary in gold

Quantitative X-ray diffraction techniques have been used to determine the structure of the large angle ∑ = 5( θ = 36.9°)[001]twist boundary in Au to a resolution of better than ±0.09Å. Large portions of the reciprocal lattice in three dimensions were mapped out using synchrotron radiation. The atomic structure was obtained by testing model structures against the intensity observations with a χ 2 analysis. Details of the atomic structure of the grain boundary, including measurement of the magnitude of the expansion at the interface, are presented. The grain boundary structure was shown to consist of arrays of two kinds of distorted octahedra and special configurations of distorted tetrahedra interwoven together by the boundary symmetry. This work points to the possibility of obtaining Pauling's type rules for grain boundary structures based on X-ray diffraction observations that give the atomic positions with high resolution. Studies were performed to search for diffraction effects that are expected to be caused by structural multiplicity of the boundary, and no evidence for its occurrence was found.

Experimental measurement of the thermal displacive properties of a large-angle twist grain boundary in gold.

Quantitative x-ray diffraction techniques have been used to estimate the mean square thermal displacements of atoms in the interface region, and to measure the thermal expansion coefficients parallel and normal to the interface plane for the large-angle $\ensuremath{\Sigma}=13$ ($\ensuremath{\theta}=22.6\ifmmode^\circ\else\textdegree\fi{}$) [001] twist grain boundary in Au. The thermal properties of the grain boundary are shown to be much different from those of the bulk material, which indicates that the effective interatomic potential for an atom in the grain boundary is different from that in bulk Au.

The Atomic Structure of Large Angle Grain Boundaries Determined by Quantitative X-Ray Diffraction Techniques

The Atomic Structure of Large Angle Grain Boundaries Determined by Quantitative X-Ray Diffraction Techniques

Observation of diffuse steaks in Au-Fe alloys utilizing synchrotron radiation

In order to fully understand the magnetic behavior of Au-Fe alloys, it is necessary to understand both the magnetic structure and the local atomic arrangements exhibited by them. For this alloy system any heat treatment involving quenching from the solid solution phase field will produce something other than a perfect binary solid solution for all but the lowest Fe concentrations. The goal of the present work was to determine the dimensions of the diffuse streaks by means of a quantitative x-ray diffraction technique using monochromatic synchrotron radiation. For a Au-18at.%Fe single crystal examined by a quantitative x-ray diffraction technique, the presence of diffuse streaks has been confirmed. The slightly higher intensities at the special points are believed to be caused by the intersection of four linking streaks rather than to superlattice peaks. The diffuse intensity pattern can be explained by the model of platelets along /420/ planes as originally proposed by Dartyge et al. The average size of the platelets is estimated to be 1.6 nm. Because of the abrupt ending of the diffuse streaks it is concluded that the platelets are at least two atomic layers thick. The results for a Au-10.7at.%Fe single crystal are lessmore » clear.« less

Thausamine in failed cement mortars and renders from exposed brickwork

The mineral thaumasite occurs within certain cement-based building materials as a direct result of sulphate attack. It readily forms within certain types of brickwork and not only contributes to expansive cracking of the brickwork but is also accompanied by severe softening of the cement matrix. Samples were taken of both brickwork mortars and renders, some of which were still relatively sound whereas others had deteriorated into a paste. The mortar samples were investigated using a quantitative Xray diffraction technique in order to determine the amounts of thaumasite, ettringite and gypsum present. Results show that if conditions are favourable then thaumasite formation can proceed rapidly and can even result in the complete breakdown of very strong renders.

Kinetics of the thermal decomposition of kyanite

Abstract The kinetics of the solid state high-temperature transformation of kyanite (Al2SiO5Al2O3·SiO2) powders (≤40 μm) to 3:2-mullite (3Al2O3·2SiO2) and silica (SiO2 were investigated by means of quantitative X-ray diffraction techniques. The transformation interval was found to lie between about 1150 and 1350°C. The reaction law best fitting the kinetic data is: 1-α = kta. The transformation is believed to be reconstructive, with decomposition of the kyanite structure, solid-state atom diffusion, and (epitactic) rearrangement of mullite and cristobalite. Cristobalite represents part of the ⪡free⪢ silica, the rest being present as a glassy phase. Addition of Fe2O3 and TiO2 to the starting material exerts a marked decrease of the transformation temperature, with TiO2 having a somewhat stronger influence than Fe2O3. The reason may be an oxide-catalyzed reaction; the decomposition begins at nuclei formed at the surfaces of the kyanite particles, which are coated with thin layers of hematite and rutile respectively.

The effect of weathering in the silt fractions on the apparent stability of chlorite in Scottish soil clays

Previous work on chloritic soils in Scotland indicated that, irrespective of soil type or drainage class, the chlorite that was dominant in the clay fractions weathered only slightly, showing little variation in amount with depth. These soils have been investigated further by determination of the chlorite content in the silt fractions by a quantitative X-ray diffraction technique. In a Dystric Cambisol and a Placic Podzol, the fine silt fractions (1.4–20 μm) contain much more chlorite than the coarse silt (20–75 μm) and in both fractions the amount of chlorite decreases towards the surface, markedly so in the Placic Podzol. It is suggested that chlorite is being dissolved out from the clay fractions but as chlorite is being broken down and transferred to finer particle size fractions, this dissolution effect is being masked by the replacement of the clay fraction chlorite from the fine silt. Analysis of the total soils (<22 mm) confirmed the net loss of chlorite from these profiles.

Kinetics of the thermal decomposition of kyanite

The kinetics of the solid state high-temperature transformation of kyanite (Al 2SiO 5Al 2O 3·SiO 2) powders (≤40 μm) to 3:2-mullite (3Al 2O 3·2SiO 2) and silica (SiO 2 were investigated by means of quantitative X-ray diffraction techniques. The transformation interval was found to lie between about 1150 and 1350°C. The reaction law best fitting the kinetic data is: 1-α = kt a. The transformation is believed to be reconstructive, with decomposition of the kyanite structure, solid-state atom diffusion, and (epitactic) rearrangement of mullite and cristobalite. Cristobalite represents part of the ⪡free⪢ silica, the rest being present as a glassy phase. Addition of Fe 2O 3 and TiO 2 to the starting material exerts a marked decrease of the transformation temperature, with TiO 2 having a somewhat stronger influence than Fe 2O 3. The reason may be an oxide-catalyzed reaction; the decomposition begins at nuclei formed at the surfaces of the kyanite particles, which are coated with thin layers of hematite and rutile respectively.

Determination of omega phase volume fraction in single crystals of beta titanium alloys

Single crystals of metastable BCC Ti-6.5 at.% Mo alloy have been aged at 350°C for varying times to precipitate the omega phase. The variation in volume fraction of precipitate was determined by a quantitative X-ray diffraction technique and correlated with transmission electron microscopy from thin foils. For Ti-Mo alloys the lattice misfit between omega and beta phases is small; reflections from parallel planes of both phases overlap necessitating the use of reflections from nonparallel planes. The 310 beta reflection and 31 4 1 and 30 3 2 omega reflections were selected. These two omega reflections occurred at 96° and 105° 2θ angles with CuKα radiation and required a 14° reorientation of the crystal.

The oxidation mechanism of Ni3Al containing yttrium

The high-temperature oxidation behavior of Ni3Al (Ni-13.2 wt.% Al) with and without additions of 0.5 wt.% yttrium has been studied over the range of 900–1200°C in air. None of the commonly accepted rate laws were followed by the kinetics. Although the weight gains of samples containing yttrium were consistently 10–20% greater than those without yttrium, the steady-state scaling rates were identical. A quantitative x-ray diffraction technique was used to determine the kinetics of growth of the protective alpha-alumina layer (one of several oxides formed). The alumina growth followed the parabolic rate law under all conditions studied. The rate-controlling transport process in alumina was the enhanced diffusion of oxygen down grain boundaries. The presence of yttrium as nickel-rich intermetallics promoted the formation of nickel aluminate (spinel). A marked increase in scale adherence was observed for short times. At longer times, however, the outer layer of spinel and unreacted nickel oxide spalled off along with some of the inner alumina layer. Loss of adherence was caused by a complex yttrium-aluminum oxide which formed by the solid-state reaction of yttria and alumina. The poor scale adherence on Ni3Al was due to the formation of voids at the alloy-oxide interface. These voids concentrated the athermal stresses above the oxide-to-metal adherence strength. The voids were produced as a result of the selective oxidation of aluminum resulting from a “Kirkendall” effect in the substrate. During the selective oxidation process, a vacancy flux directed from the matrix to the metaloxide interface resulted in a supersaturation of vacancies. Equilibrium was maintained by the condensation of excess vacancies. The presence of yttrium as either nickel-rich intermetallics or internal oxide prevented the voids from forming. The yttrium-rich particles relieved the matrix of vacancy supersaturation by providing vacancy sinks. The chemical nature of the particles does not seem important. A necessary and sufficient condition for an effective vacancy sink appears to be the presence of an incoherent boundary between particle and matrix.